Embedded sensor response linearization method

Abstract

In embodiments disclosed herein, a method for calibrating a photonic sensor includes collecting a plurality of concentration measurements with a photonic sensor with a plurality of different reference gas mixtures under various temperature and pressure environments, where each reference gas mixture includes a known species concentration, and implementing a parameter optimization routine to minimize deviations between the known species concentrations and the plurality of concentration measurements obtained by the photonic sensor, where the optimization routine generates one or more calibration constants. In an embodiment, the method may further include integrating the one or more calibration constants into a modified concentration formula, and storing the modified concentration formula in a controller used to operate the photonic sensor.

What is claimed is: 
     
         1 . A method for calibrating a photonic sensor, comprising:
 collecting a plurality of concentration measurements with the photonic sensor with a plurality of different reference gas mixtures, wherein each reference gas mixture comprises a known species concentration;   implementing a parameter optimization routine to minimize deviations between the known species concentrations and the plurality of concentration measurements obtained by the photonic sensor, wherein the parameter optimization routine generates one or more calibration constants;   integrating the one or more calibration constants into a modified concentration formula; and   storing the modified concentration formula in a memory.   
     
     
         2 . The method of  claim 1 , wherein the parameter optimization routine comprises a Chi-square minimization. 
     
     
         3 . The method of  claim 1 , wherein the one or more calibration constants comprises a coefficient. 
     
     
         4 . The method of  claim 1 , wherein the one or more calibration constants comprise an exponent. 
     
     
         5 . The method of  claim 1 , wherein the modified concentration formula provides a linearization of a relationship between the concentration measurements and the known species concentration. 
     
     
         6 . The method of  claim 5 , wherein the relationship is approximately 1:1 with a deviation of up to 0.05%. 
     
     
         7 . The method of  claim 6 , wherein the deviation is up to 0.02%. 
     
     
         8 . The method of  claim 1 , wherein the plurality of concentration measurements are made over one or more of a temperature range, a concentration range, or a pressure range. 
     
     
         9 . The method of  claim 8 , wherein the temperature range is between 20° C. and 120° C. and the pressure range is between 50 Torr and 150 Torr. 
     
     
         10 . The method of  claim 1 , wherein the photonic sensor is a non-dispersive optical sensor that operates with electromagnetic radiation with a wavelength from ultraviolet (UV) to infrared (IR). 
     
     
         11 . An apparatus, comprising:
 a gas cell-body with a first end and a second end;   a light source coupled to the first end of the gas cell-body, wherein the light source is configured to propagate electromagnetic radiation through the gas cell-body;   a photonic detector coupled to the second end of the gas cell-body;   a controller coupled to the photonic detector, wherein a processor of the controller is configured to convert intensity signals from the photonic detector into species concentrations through a use of a modified concentration formula;   a housing around the gas cell-body that is temperature controlled, wherein the photonic detector is outside the housing;   a temperature sensor configured to measure a temperature of gas that flows through the gas cell-body; and   a pressure sensor configured to measure a pressure within the gas cell-body.   
     
     
         12 . The apparatus of  claim 11 , wherein the modified concentration formula comprises one or more calibration constants. 
     
     
         13 . The apparatus of  claim 12 , wherein the one or more calibration constants comprise one or both of a coefficient or an exponent. 
     
     
         14 . The apparatus of  claim 11 , wherein the modified concentration formula is stored in the controller as part of one or more of a hardware component, a firmware component, or a software component. 
     
     
         15 . The apparatus of  claim 11 , wherein the photonic detector is an infrared photo-detector or an ultraviolet photo-detector. 
     
     
         16 . The apparatus of  claim 11 , further comprising:
 an inlet proximate to the first end the gas cell-body for flowing the gas into the gas cell-body, wherein the inlet is fluidically coupled to an ampoule; and   an outlet proximate to the second end of the gas cell-body for flowing the gas out of the gas cell-body, wherein the outlet is fluidically coupled to a processing chamber.   
     
     
         17 . The apparatus of  claim 11 , wherein the apparatus is a non-dispersive infrared (NDIR) sensor or a non-dispersive ultraviolet (NDUV) sensor. 
     
     
         18 . A method of measuring a concentration of a species in a gas, comprising:
 flowing the gas from an ampoule to a chamber;   measuring an intensity signal of the species in the gas with a photonic sensor between the ampoule and the chamber; and   converting the intensity signal into the concentration of the species through an application of a modified concentration formula that comprises one or more calibration constants.   
     
     
         19 . The method of  claim 18 , wherein the photonic sensor is a non-dispersive infrared optical sensor that operates with electromagnetic radiation with a wavelength from infrared (IR) to ultraviolet (UV). 
     
     
         20 . The method of  claim 18 , wherein the modified concentration formula is a result of a parameter optimization.